Monday Seminar Talk (short) 17 November, 2003

Taro Morimoto

Abstract

The solar polarity reversal

The cessation of high latitude CMEs

Close Relationship

- based on the observations for cycles 21 & 23.

The polar crown filaments need to be removed before the poles could acquire open field structure of the opposite polarity.

Because :

IntroductionDisappearance and reformation of polar coronal holes. (Webb, Davis & McIntosh 1984; Bilenko 2002; Harvey & Recely 2002)

Disappearance of polar crown filaments(PCF).(Waldmeier 1960; Makarov, Tlatov & Sivaraman 2001)

Goplaswamy et al.(2003) Prominence eruptions at high latitudes subsided around the time of the polarity reversals. (From SOHO/LASCO & NoRH observations)

IntroductionUsing CME data of cycles 21 & 23, they tested how CMEs are intimately connected to the mechanism of polarity reversal.

Data

21

CME

Solwind

23 SOHO/LASCO

Prominence Eruption (PE)

Nobeyama radio heliograph

Kitt Peak magnetograph measurements for polar region magnetic field strength

PE and CMEs

epochs of cessation of HL activity (north; : south)

HCS

HCS Max. excursions of heliospheric current sheet. (from Wilcox Obs.)

North-south asymmetry in the high latitude (HL) activities.

CME occurence rate

HL : High Latitude ( 60°) [PCF-related = 1159 CMEs]≧LL : Low Latitude ( 40°) [AR-related = 4607 CMEs]≦SSN: daily Sun Spot Number

CME peakSSN peak

Cycle 23

01

3

3

05 1003 10month:

North South

Northern HL(NHL)

HL CME peakmid/99 A rapid increase

03/00 – 09/00 A broad maximum

Polar field reversal: 10/00 from data

02/01 (Bilenko 2002)

05/01 (Durrant & Wilson 2003)

PCF disappearance10/00 (Harvey & Recely 2002; Lorenc, Pasorek & Rybansky 2003; Gopalswamy et al. 2003)

Disappearance of PCF

Cycle 23

01

3

3

05 1003 10month:

North South

Southern HL(SHL)

HL CME peakmid/99 – 03/02

Polar field reversal: 05/01 from data

09/01 (Durrant & Wilson 2003)

01/02 (Bilenko 2002)

PCL disappearance02/02 (Lorenc et al. 2003)

04/02 (Harvey & Recely 2002)

Disappearance of PCF

Cycle 21

3

3

North South

Northern HL(NHL)

Disappearance of PCF

Polar field reversal: 02/82- 03/82 (Webb et al.1984)

09/80 & 07/82 from data.

PCL disappearance ① Webb et al. 1984

② Lorenc et al. 2003

①②

HL CME peaklight blue shadow region

Cycle 21

3

3

North South

Southern HL(SHL)

Disappearance of PCF

Polar field reversal: 09/80 (Webb et al. 1984)

02/83 from data.

PCL disappearance ① Webb et al. 1984

② Lorenc et al. 2003

① ②

HL CME peak(pink shadow region)

SummaryThe epochs of solar polar reversal are closely related to the cessation of HL CME activities.

Before the completion of the reversal, several temporary reversals take place with corresponding spikes in the HL CME rates.

The North-South asymmetry of the polarity reversal time and HL activity is of high importance. The CME process helps the closed field lines overlying PCFs become open to complete the polarity reversal. (c.f.: Low (1997))